Many industries designate their products with optically readable information. Optically readable information often takes the form of a bar code symbol consisting of a series of lines and spaces of varying widths. Various bar code readers and laser scanning systems have been employed to decode such symbol patterns. One of the many problems encountered in the bar code reader art, wherein a photosensitive array are utilized, is to produce an optical system capable of focusing images of optically readable information where such information lies at varying distances from the reader.
Known to the art are readers which utilize mechanical means to change the focal length of an optical system. Although such mechanical means may be employed to read optical information over a substantial range of distances, such means are often somewhat cumbersome in design, temperamental, expensive, and require the expenditure of additional battery energy. Thus, in the hand-held optical information reader art, where power consumption, weight, portability, convenience, range, and depth-of-field are of great concern, means for obviating and simplifying focusing requirements have long been sought.
Therefore, it is a principal object of the present invention to provide a method and apparatus for focusing an image of optical information over a substantial range of distances which requires no moving parts, is convenient, easy to use and simple in construction.
Another object of the present invention is to provide a method and apparatus for focusing an image of optical information over a substantial range of distances which is compact in design.